Grade ix input and output devices

Made By : Sofiya Malek
Grade IX
Topic: Input/Output Devices

Introduction
 The computer will be of no use unless it is able to
communicate with the outside world. Input/Output devices
are required for users to communicate with the computer.
In simple terms, input devices bring information INTO the
computer and output devices bring information OUT of a
computer system. These input/output devices are also
known as peripherals since they surround the CPU and
memory of a computer system. Some commonly used
Input/Output devices are listed in table below.
 Input Devices
 Keyboard ,Mouse, Joystick ,Scanner, Light Pen, Touch Screen
 Output Devices
 Monitor LCD Printer Plotter

Key board
It is a text base input device that allows the user to
input alphabets, numbers and other characters.
It consists of a set of keys mounted on a board.

Key board
It consists of,
1. Alphanumeric keys
2. Function Keys :These keys are also user
programmable keys.
3. Special-function Keys :
Enter ,Spacebar ,Backspace, Delete, Insert, Shift,
Caps Lock,
Tab, Ctrl, Alt , Esc
1. Numeric Keypad
2. Cursor Movement Keys

keyboard
 keyboard is a typewriter style, which uses an arrangement of
buttons or keys, to act as mechanical levers or electronic
switches.
 A keyboard typically has characters engraved or printed on the
keys and each press of a key typically corresponds to a single
written symbols. However, to produce some symbols requires
pressing and holding several keys simultaneously or in
sequence. While most keyboard keys
produce letters,numbers or signs (characters), other keys or
simultaneous key presses can produce actions or execute
computer commands.
 Despite the development of alternative input devices, such as
the mouse, touch screen, pen devices, character
recognition and voice recognition, the keyboard remains the
most commonly used and most versatile device used for direct
(human) input into computers.
 To know more about working of keyboard, visit the link
below:

mouse
 A pointing device is an human interface device that allows a
user to input spatial data to a computer. In the case of mouse
and touchpads, this is usually achieved by detecting
movement across a physical surface.
 The rubber ball at the bottom of the mouse get the movement
by moving the mouse on the surface which will move internal
rollers and give the movement to the pointer on the screen
such as left right or up and down.
 A mouse includes left button, right button and sometimes scroll
wheel)
 The newer optical mouse uses light and small optical sensor
to detect the motion of the mouse by tracking a tiny image of
the desk surface. It avoids the problem of dirty mouse ball.
 Cordless or wireless mouse communicates with the computer
via radio waves. It needs internal batteries.
 To know more about working of mouse, visit the link below:

JOYSTICK
 A joystick is an input device consisting of a stick that pivots
on a base and reports its angle or direction to the device it
is controlling. A joystick, also known as the control column,
is the principle control device in the cockpit of many civilian
and military aircraft, either as a center stick or side-stick.
 The difference between mouse and joystick is that with the
mouse cursor stops moving as soon as you stop moving the
mouse. With joystick the pointer continues moving in the
direction the joystick is pointing.
 It often has supplementary switches to control various
aspects of the aircraft's flight.
 Joysticks are often used to control video games, and
usually have one or more push-buttons whose state can
also be read by the computer.
 Joysticks are also used for controlling machines such as
cranes, trucks, underwater unmanned vehicles,
wheelchairs, surveillance cameras, and zero turning radius
lawn mowers.
 To know more about working of joystick, visit the link
below:
 https://electronics.howstuffworks.com/joystick.htm

BARCODE READER
 A barcode is a screen of black strips of
various thicknesses on a white background.
Barcodes are use to keep track of large
quantity of items, such as products in shops
or books in a library.
 A barcode reader (or barcode scanner) is
an electronic device for reading
printed barcodes.
 It consists of a light source, a lens and a
light sensor translating optical impulses into
electrical ones.
 Additionally, nearly all barcode readers
contain decoder circuitry analyzing the
barcode's image data provided by the
sensor and sending the barcode's content
to the scanner's output port.
 To know more about working of barcode

MICROPHONE
 A microphone converts sound in air into
an electrical signal. Microphones are used
in many applications such as telephones,
tape, recorders, karaoke systems, hearing
aids, motion picture production,
in radio and television broadcasting and in
computers for recording voice,speech
recognition.
 Voice speech reorganization would
eliminate the need for keying in data and
would facilitate untrained users to use the
computer very easily and for handicapped
person also.
 To know more about microphone, click on
link given below:

TRACK BALL
 A trackball is like an upside-down mouse with
an exposed protruding ball. The user rolls the
ball with the thumb, fingers, or the palm of
the hand to move a pointer.
 Compared with a mouse, a trackball has no
limits on effective travel; at times, a mouse can
reach an edge of its working area while the
operator still wishes to move the screen pointer
farther. With a trackball, the operator just
continues rolling, whereas a mouse would have
to be lifted and re-positioned. The trackball's
buttons may be situated to that of a mouse or to
a unique style that suits the user.
 Large trackballs are common
on CAD workstations for easy precision. Before
the advent of the touchpad, small trackballs
were common on portable computers, where
there may be no desk space on which to run a
mouse. Some small thumb balls clip onto the
side of the keyboard and have integral buttons
with the same function as mouse buttons.

TOUCH SCREEN
 A touch screen is an electronic visual display that the user can control through simple
or multi-touch gestures by touching the screen with a special stylus/pen and-or one or
more fingers. Some touch screens use an ordinary or specially coated gloves to work
while others use a special stylus/pen only. The user can use the touch screen to react
to what is displayed and to control how it is displayed (for example by zooming the
text size).
 The touch screen enables the user to interact directly with what is displayed, rather
than using a mouse, touchpad, or any other intermediate device.
 Touch screens are common in devices such as game consoles, all-in-one
computers, tablet computers, and smart phones. They can also be attached to
computers or, as terminals, to networks. They also play a prominent role in the design
of digital appliances such as personal digital assistants (PDAs), satellite
navigation devices, mobile phones, and video games and some books (Electronic
books).
 The popularity of smart phones, tablets, and many types of information appliances is
driving the demand and acceptance of common touch screens for portable and
functional electronics. Touch screens are found in the medical field and in heavy
industry, as well as for automated teller machines (ATMs), and kiosks such as
museum displays or room automation, where keyboard and mouse systems do not
allow a suitably intuitive, rapid, or accurate interaction by the user with the display's
content.
 To know more about touch screen click on link below:

LIGHT PEN
 A light pen is a computer input
device.
 It allows the user to point to
displayed objects or draw on the
screen in a similar way to a touch
screen but with greater positional
accuracy.
 There are two types of Light Pen-
one type is used to draw on special
screen. The other type of Light pen
is used to read information from Bar
codes. It sends signals to the
computer according to the
thickness of the blank lines it
passes over.

SCANNER
 scanner is a device that optically scans images, printed
text, handwriting, or an object, and converts it to a digital image.
Commonly used in offices are variations of the desktop flatbed
scanner where the document is placed on a glass window for
scanning. Mechanically driven scanners that move the
document are typically used for large-format documents, where a
flatbed design would be impractical.
 If we want to convert any image file(basically which is text file)
into text file we need to run it through OCR(optical character
recognition) software that identifies the individual letter shapes
and creates a text file of the page’s content.
 Digital cameras can be used for the same purposes as dedicated
scanners. When compared to a true scanner, a camera image is
subject to a degree of distortion, reflections, shadows, low
contrast, and blur due to camera shake (reduced in cameras with
image stabilization). Resolution is sufficient for less demanding
applications. Digital cameras offer advantages of speed,
portability and non-contact digitizing of thick documents without
damaging the book spine

TOUCH PAD
 A touchpad or trackpad is a pointing
device featuring a tactile sensor, a
specialized surface that can translate
the motion and position of a user's
fingers to a relative position on the
operating system that is outputted to
the screen. Touch pads are a
common feature of laptop computers,
and are also used as a substitute for
a mouse where desk space is scarce.
Because they vary in size, they can
also be found on personal digital
assistants (PDAs) and some portable
media players. Wireless
touchpads are also available as
detached accessories. In recent years
the term "touchpad" is falling out of
favor in exchange for "track pad," as
the term "touchpad" is often confused
with tablet PCs or "convertible" touch

GRAPHICS TABLET
 A graphics tablet or digitizer is a
computer input device that enables a user
to hand-draw images, animations and
graphics, similar to the way a person draws
images with a pencil and paper. These
tablets may also be used to capture data or
handwritten signatures. It can also be used
to trace an image from a piece of paper
which is taped or otherwise secured to the
surface. Capturing data in this way, either
by tracing or entering the corners of linear
poly-lines or shapes is called digitizing.
 The device consists of a flat surface upon
which the user may "draw" or trace an
image using an attached a pen-like
drawing apparatus. The image is displayed
on the computer monitor, although some
graphics tablets also have a screen.

OMR (Optical Mark Reader)
 OMR is an input device that reads different marks, codes and then converts
them into computer readable form.
 OMR is generally distinguished from optical character recognition (OCR) by
the fact that a complicated pattern recognition engine is not required. That is,
the marks are constructed in such a way that there is little chance of not
reading the marks correctly.
 One of the most familiar applications of optical mark recognition is the use
of #2 pencil (HB in Europe) bubble optical answer sheets in multiple choice
question examinations. Students mark their answers, or other personal
information, by darkening circles marked on a pre-printed sheet. Afterwards
the sheet is automatically graded by a scanning machine.
 Many of today's OMR applications involve people filling in specialized forms.
These forms are optimized for computer scanning, with careful registration in
the printing, and careful design so that ambiguity is reduced to the minimum
possible. Due to its extremely low error rate, low cost and ease-of-use, OMR
is a popular method of tallying votes.
 To know more about “how OMR worksheets are checked?”, click on link
given below

OCR
 Optical Character Recognition, usually abbreviated to OCR, is
the mechanical or electronic conversion of scanned images of
typewritten or printed text into machine-encoded/computer-readable
text.
 It is widely used as a form of data entry from some sort of original
paper data source.
 Early versions needed to be programmed with images of each
character, and worked on one font at a time. "Intelligent" systems
with a high degree of recognition accuracy for most fonts are now
common. Some commercial systems are capable of reproducing
formatted output that closely approximates the original scanned page
including images, columns and other non-textual components.
 These characters may be either typewritten or hand written or
computer written. For example, the OCR devices include the reading
of zip codes by the U S postal services, the reading of passenger
tickets and freights bills by airlines, and the processing of social
security forms and motor vehicle registrations by governments.
 To know more about working of OCR , click on given link below:
 https://youtu.be/gQER4iTeYNY

MICR (Magnetic ink character
recognition)
 MICR is a character-recognition
technology used mainly by the
banking industry to ease the
processing and clearance of
cheques and other documents. The
MICR encoding, called the MICR
line, is at the bottom of cheques and
other vouchers and typically
includes the document-type
indicator, bank code, bank account
number, cheque number, cheque
amount, and a control indicator. The
technology allows MICR readers to
scan and read the information
directly into a data-collection device.
Unlike barcodes and similar
technologies, MICR characters can
be read easily by humans.

MIDI(Musical Instrument Digital
Interface)
 MIDI is a system designed to transmit
information between electronic musical
instruments. A MIDI musical keyboard can
be attached to a computer and allows a
performer to play music that is captured
by the computer system as a sequence of
notes with the associated timing (instead
of recognizing digitized sound waves).
 MIDI technology was standardized in
1983 by a panel of music industry
representatives, and is maintained by
the MIDI Manufacturers
Association(MMA).
 Advantages of MIDI include compactness
(an entire song can be coded in a few
hundred lines, i.e. in a few kilobytes),

DIGITAL CAMERA
 A digital camera (or digicam) is
a camera that encodes digital
images and videos digitally and
stores them for later
reproduction. Most cameras sold
today are digital and digital cameras
are incorporated into many devices
ranging from PDAs and mobile
phones (called camera phones).
 It contains a lens, an aperture and a
shutter. The lens brings light from the
scene into focus inside the camera so
it can expose an image. The
aperture is a hole that can be made
smaller or larger to control the
amount of light entering the camera.
The shutter is a device that can be
opened or closed to control the length
of time the light enters.

WEB CAMERA
 A webcam is a video camera that feeds
or streams its image in real time to or
through a computer or computer network.
When "captured" by the computer, the video
stream may be saved, viewed or sent on to
other networks via systems such as the
internet, and email as an attachment. When
sent to a remote location, the video stream
may be save, viewed or on sent there.
 A webcam is generally connected by
a USB cable or built into computer
hardware, such as laptops.
 Webcams are known for their
low manufacturing cost and
flexibility, making them the lowest cost form
of videotelephony. They have also become
a source of security and privacy issues.

OUTPUT DEVICES
MONITOR
 The VDU(Visual Display Unit) is also called a monitor or
screen. Messages and processed information are also
displayed on the screen.
 There are two types of display terminals.
 Alphanumeric display
 Graphical Display
 There are three classification on the basis of color
capabilities.
 MONOCROME: displays two colors, one for background
and one for foreground. The colors can be black and white,
green and black or amber and black.
 GRAY-SCALE: displays different type of grays.
 COLOR: displays from 16 to over 1 million different colors.
Also called RGB monitors because they accept three
separate signals- red, green and blue.

MONITOR
 Early electronic computers were fitted with a panel of light bulbs
where the state of each particular bulb would indicate the on/off
state of a particular register bit inside the computer. This allowed
the engineers operating the computer to monitor the internal
state of the machine, so this panel of lights came to be known as
the 'monitor'. As early monitors were only capable of displaying a
very limited amount of information, and were very transient, they
were rarely considered for programme output. Instead, a line
printer was the primary output device, while the monitor was
limited to keeping track of the programme's operation.
 In time this array of light bulbs was replaced by a cathode ray
tube which could display the equivalent of several dozen light
bulbs with greater reliability.
 As technology developed it was realised that the output of a CRT
display was more flexible than a panel of light bulbs and
eventually, by giving control of what was displayed to the
programme itself, the monitor itself became a powerful output
device in its own right.
 To know about how Monitor works, click on given link below:
 https://computer.howstuffworks.com/monitor.htm

CRT(Cathode ray tube)
 The first computer monitors used cathode ray
tubes (CRT). Prior to the advent of home
computers in the late 1970s, CRTs – also known as
video display terminals (VDT)
 The monitors were monochrome and the image
quality was generally poor compared to current
displays.
 The capabilities provided by the combination of the
CRT and computer systems driving it have increased
in capability progressively over the years in step with
the general increase in the computer industry's
technological capability. In 1984 IBM introduced
the Enhanced Graphics Adapter which was capable of
producing 16 colors and had a resolution of 640 by
350.
 CRT technology remained dominant in the PC monitor
market into the new millennium partly because it was

LCD(Liquid crystal display)
 There are multiple technologies that have been used to implement liquid
crystal displays (LCD). Throughout the 1990s, the primary use of LCD
technology as computer monitors was in laptops where the lower power
consumption, lighter weight, and smaller physical size of LCDs justified the
higher price versus a CRT. Commonly, the same laptop would be offered
with an assortment of display options at increasing price points: (active or
passive) monochrome, passive color, or active matrix color (TFT). As volume
and manufacturing capability have improved, the monochrome and passive
color technologies were dropped from most product lines.
 TFT-LCD is a variant of LCD which is now the dominant technology used for
computer monitors.[3]
 The first standalone LCD displays appeared in the mid-1990s selling for high
prices. As prices declined over a period of years they became more popular,
and by 1997 were competing with CRT monitors. Among the first desktop
LCD computer monitors was the Eizo L66 in the mid-1990s, the Apple Studio
Display in 1998, and the Apple Cinema Display in 1999. In 2003, TFT-LCDs
outsold CRTs for the first time, becoming the primary technology used for
computer monitors.[2] The main advantages of LCDs over CRT displays are
that LCDs consume less power, take up much less space, and are
considerably lighter. The now common active matrix TFT-LCD technology

LED
 light-emitting diode[edit]
 light-emitting diode (LED) monitors provide higher
contrast and better viewing angles than LCDs but
they require more power when displaying
documents with white or bright backgrounds. In
2011, a 25-inch (64 cm)LED monitor cost $7500,
but the prices are expected to drop.[6]

IMPACT PRINTER
 Impact printers rely on a forcible impact to transfer ink to the media.
The impact printer uses a print head that either hits the surface of the
ink ribbon, pressing the ink ribbon against the paper (similar to the
action of a typewriter), or hits the back of the paper, pressing the paper
against the ink ribbon (the IBM 1403 for example). All but the dot matrix
printer rely on the use of fully formed characters, letterforms that
represent each of the characters that the printer was capable of printing.
In addition, most of these printers were limited to monochrome, or
sometimes two-color, printing in a single typeface at one time,
although bolding and underlining of text could be done by "overstriking",
that is, printing two or more impressions in the same character position.
Impact printers varieties include, typewriter-derived printers,
teletypewriter-derived printers, daisy wheel printers, dot matrix printers
and line printers. Dot matrix printers remain in common use in
businesses where multi-part forms are printed, such as car rental
services. An overview of impact printing[4] contains a detailed
description of many of the technologies used.
 Pen-based plotters were an alternate printing technology once common
in engineering and architectural firms. Pen-based plotters rely on
contact with the paper (but not impact, per se) and special purpose
pens that are mechanically run over the paper to create text and
images.

DAISY WHEEL PRINTER
 Daisy wheel printers[edit]
 Main article: Daisy wheel printer
 "daisy wheel" print element
 Daisy wheel printers operate in much
the same fashion as a typewriter. A
hammer strikes a wheel with petals,
the "daisy wheel", each petal
containing a letter form at its tip. The
letter form strikes a ribbon of ink,
depositing the ink on the page and
thus printing a character. By rotating
the daisy wheel, different characters
are selected for printing. These printers
were also referred to as letter-quality
printers because they could produce
text which was as clear and crisp as a
typewriter. The fastest letter-quality
printers printed at 30 characters per

DOT MATRIX PRINTER
 Dot-matrix printers[edit]
 Main article: Dot matrix printer
 sample output from 9-pin dot matrix printer (one character expanded to show detail)
 The term dot matrix printer is used for impact printers that use a matrix of small pins to transfer ink to the page. The advantage of dot
matrix over other impact printers is that they can produce graphical images in addition to text; however the text is generally of poorer
quality than impact printers that use letterforms (type).
 Dot-matrix printers can be broadly divided into two major classes:
 Ballistic wire printers
 Stored energy printers
 Dot matrix printers can either be character-based or line-based (that is, a single horizontal series of pixels across the page), referring to the
configuration of the print head.
 In the 1970s & 80s, dot matrix printers were one of the more common types of printers used for general use, such as for home and small
office use. Such printers normally had either 9 or 24 pins on the print head (early 7 pin printers also existed, which did not print
descenders). 24-pin print heads were able to print at a higher quality. Once the price of inkjet printers dropped to the point where they were
competitive with dot matrix printers, dot matrix printers began to fall out of favor for general use.
 Some dot matrix printers, such as the NEC P6300, can be upgraded to print in colour. This is achieved through the use of a four-colour
ribbon mounted on a mechanism (provided in an upgrade kit that replaces the standard black ribbon mechanism after installation) that
raises and lowers the ribbons as needed. Colour graphics are generally printed in four passes at standard resolution, thus slowing down
printing considerably. As a result, colour graphics can take up to four times longer to print than standard monochrome graphics, or up to 8-
16 times as long at high resolution mode.
 Dot matrix printers are still commonly used in low-cost, low-quality applications like cash registers, or in demanding, very high volume
applications like invoice printing. The fact that they use an impact printing method allows them to be used to print multi-part documents
using carbonless copy paper, like sales invoices and credit card receipts, whereas other printing methods are unusable with paper of this
type. Dot-matrix printers are now (as of 2005) rapidly being superseded even as receipt printers.
 Line printers[edit]

THERMAL PRINTER
 Thermal printing (or direct thermal printing) is
a digital printing process which produces a printed
image by selectively heating coated thermochromic
paper, orthermal paper as it is commonly known,
when the paper passes over the thermal print head.
The coating turns black in the areas where it is
heated, producing an image. Two-colour direct
thermal printers can print both black and an
additional colour (often red) by applying heat at two
different temperatures.
 Thermal transfer printing is a very different method
that uses a heat-sensitive ribbon instead of heat-
sensitive paper, but uses similar thermal print
heads.[1]
 Thermal printing is notable for being the only[verification
needed] form of (non-embossing) printing which involves

DESIGN
 Design[edit]
 A thermal printer comprises these key components:
 Thermal head: generates heat; prints on paper
 Platen: a rubber roller that feeds paper
 Spring: applies pressure to the thermal head, causing it to contact the thermosensitive paper
 Controller boards: for controlling the mechanism
 In order to print, thermo-sensitive paper is inserted between the thermal head and the platen.
The printer sends an electrical current to the heating elements of the thermal head, which
generate heat. The heat activates the thermo-sensitive coloring layer of the thermosensitive
paper, which changes color where heated. Such a printing mechanism is known as a thermal
system or direct system. The heating elements are usually arranged as a matrix of small
closely spaced dots—thermal printers are actually dot-matrix printers, though they are not so
called.
 The paper is impregnated with a solid-state mixture of a dye and a suitable matrix; a
combination of a fluoran leuco dye and an octadecylphosphonic acid is an example. When
the matrix is heated above its melting point, the dye reacts with the acid, shifts to its colored
form, and the changed form is then conserved in metastable state when the matrix solidifies
back quickly enough (a process known as thermochromism).
 Controller boards are embedded with firmware to manage the thermal printer mechanisms.
The firmware can manage multiple bar code types, graphics and logos. They enable the user
to choose between different resident fonts (also including Asian fonts) and character sizes.
Controller boards can drive various sensors such as paper low, paper out, door open and so
on, and they are available with a variety of interfaces, such as RS-
232, parallel, USBand wireless. For point of sale application some boards can also control
the cash drawer.

APPLICATION
 Thermal printers print more quietly and usually faster than impact dot matrix printers. They are also smaller,
lighter and consume less power, making them ideal for portable and retail applications. Roll-based printers
can be rapidly refilled. Commercial applications of thermal printers include filling station pumps,
information kiosks, point of sale systems, voucher printers in slot machines, print on demand labels for
shipping and products, and for recording live rhythm strips on hospital cardiac monitors.
 Many popular microcomputer systems from the late 1970s and early 1980s had first-party and aftermarket
thermal printers available for them - such as the Atari 822 printer for the Atari 8-bit systems, the Apple
Silentype for the Apple II and the Alphacom 32 for the Sinclair ZX Spectrum and ZX81. They often used
unusually-sized supplies (10CM wide rolls for the Alphacom 32 for instance) and were often used for making
permanent records of information in the computer (graphics, program listings etc.), rather than for
correspondence.
 Through the 1990s many fax machines used thermal printing technology. Toward the beginning of the 21st
century, however, thermal wax transfer, laser, and inkjet printing technology largely supplanted thermal
printing technology in fax machines, allowing printing on plain paper.
 Thermal printers are still commonly used in seafloor exploration and engineering geology due to their
portability, speed, and ability to create continuous reels or sheets. Typically, thermal printers found in
offshore applications are used to print realtime records of side scan sonar and sub-seafloor seismicimagery.
In data processing, thermal printers are sometimes used to quickly create hard copies of continuous seismic
or hydrographic records stored in digital SEG Y or XTF form.
 The Game Boy Printer, released in 1998, was a small thermal printer used to print out certain elements from
some Game Boy games.
 Early formulations of the thermo-sensitive coating used in thermal paper were sensitive to incidental
heat, abrasion, friction (which can cause heat, thus darkening the paper), light (which can fade printed
images), and water. Later thermal coating formulations are far more stable; in practice, thermally printed text
should remain legible at least 50 days.[citation needed]
 In many hospitals in the United Kingdom, many common ultrasound sonogram devices output the results of
the scan onto thermal paper. This can cause problems if the parents wish to preserve the image by
laminating it, as the heat of most laminators will darken the entire page—this can be tested for beforehand
on an unimportant thermal print. An option is to make and laminate a permanent ink duplicate of the image.

LINE PRINTER
 The line printer is an impact printer in which one
line of text is printed at a time. They are mostly
associated with unit record equipmentand the
early days of digital computing, but the
technology is still in use. Print speeds of 600
lines-per-minute (approximately 10 pages per
minute) were achieved in the 1950s, later
increasing to as much as 1200 lpm. Line printers
print a complete line at a time and have speeds in
the range of 150 to 2500 lines per minute. The
different types of line printers are drum printers
and chain printers.

LASER PRINTER
 Laser printing is an electrostatic digital printing process that rapidly
produces high quality text and graphics by passing a laser beam over a
charged drum to define a differentially charged image. The drum then
selectively collects charged toner and transfers the image to paper,
which is then heated to permanently fix the image. As with
digital photocopiers and multifunction printers (MFPs),
laser printers employ a xerographic printing process, but differ from
analog photocopiers in that the image is produced by the direct
scanning of the medium across the printer's photoreceptor. Hence, it
proves to be a much faster process compared to the latter.
 A laser beam, typically from an aluminium gallium
arsenide semiconductor laser, projects an image of the page to be
printed onto an electrically charged rotating drum coated
with selenium[6] or, more common in modern printers, organic
photoconductors. Photoconductivity allows charge to leak away from the
areas exposed to light. Powdered ink (toner) particles are
then electrostaticallypicked up by the drum's charged areas, which have
not been exposed to the laser beam. The drum then prints the image
onto paper by direct contact and heat, which fuses the ink to the paper.
 To know about the working of laser printer, click on given link below:
 https://computer.howstuffworks.com/laser-printer.htm

 Color laser printers use colored toner (dry ink),
typically cyan, magenta, yellow, and black (CMYK).
 While monochrome printers only use one laser scanner
assembly, color printers often have two or more.
 Color printing adds complexity to the printing process
because very slight misalignments known as registration
errors can occur between printing each color, causing
unintended color fringing, blurring, or light/dark streaking
along the edges of colored regions. To permit a high
registration accuracy, some color laser printers use a large
rotating belt called a "transfer belt". The transfer belt
passes in front of all the toner cartridges and each of the
toner layers are precisely applied to the belt. The
combined layers are then applied to the paper in a uniform
single step.
 Color printers usually have a higher cost per page than
monochrome printers.

 Comparison with inkjet printers[edit]
 Manufacturers use a similar business model for
both low-cost color laser printers and inkjet
printers: the printers are sold cheaply while
replacement toners and inks are relatively
expensive. Color laser printers are much quicker
than inkjet printers and their running cost per
page is usually slightly less. The print quality of
color lasers is limited by their resolution, typically
600–1200 dpi, and their use of just four color
toners. They often have trouble printing large
areas of the same or gradually changing color.
Inkjet printers designed for printing photos can
produce much higher quality color images.[9]

SPEAKER
 Computer speakers, or multimedia speakers, are speakers external
to a computer, that disable the lower fidelity built-in speaker. They
often have a low-power internal amplifier. The standard audio
connection is a 3.5 mm (approximately 1/8 inch) stereo phone
connector often color-coded lime green (following the PC 99 standard)
for computer sound cards. A few use a RCA connector for input. There
are also USB speakers which are powered from the 5 volts at 500
milliamps provided by the USB port, allowing about 2.5 watts of output
power. Computer speakers were introduced by Altec Lansing in
1990.[1]
 Computer speakers range widely in quality and in price. The computer
speakers typically packaged with computer systems are small, plastic,
and have mediocre sound quality. Some computer speakers have
equalization features such as bass and treble controls.
 The internal amplifiers require an external power source, usually
an AC adapter. More sophisticated computer speakers can have a
subwoofer unit, to enhance bass output, and these units usually
include the power amplifiers both for the bass speaker, and the small
satellite speakers.
 Some computer displays have rather basic speakers built-
in. Laptops come with integrated speakers. Restricted space available
in laptops means these speakers usually produce low-quality sound.
 For some users, a lead connecting computer sound output to an
existing stereo system is practical. This normally yields much better
results than small low-cost computer speakers. Computer speakers
can also serve as an economy amplifier for MP3 player use for those
who wish to not use headphones, although some models of computer
speakers have headphone jacks of their own.

PLOTTER
 The plotter is
a computer printer for
printing vector graphics. In the
past, plotters were used in
applications such
as computer-aided design,
though they have generally
been replaced with wide-
format conventional printers. A
plotter gives a hard copy of the
output. It draws pictures on
paper using a pen. Plotters are
used to print designs of ships
and machines, plans for
buildings and so on.

 Computer data storage, often called storage or memory,
is a technology consisting of computer components
and recording media used to retain digital data. It is a core
function and fundamental component of computers.
The central processing unit (CPU) of a computer is what
manipulates data by performing computations. In practice,
almost all computers use a storage hierarchy, which puts
fast but expensive and small storage options close to the
CPU and slower but larger and cheaper options farther
away. Often the fast, volatile technologies (which lose data
when powered off) are referred to as "memory", while
slower permanent technologies are referred to as
"storage", but these terms can also be used
interchangeably. In the Von Neumann architecture, the
CPU consists of two main parts: control unit and arithmetic
logic unit (ALU). The former controls the flow of data
between the CPU and memory; the latter performs
arithmetic and logical operations on data.

FLOPPY DISK
 A floppy disk, or diskette, is a disk storage medium
composed of a disk of thin and flexible magnetic
storage medium, sealed in a rectangular plastic carrier
lined with fabric that removes dust particles. Floppy
disks are read and written by a floppy disk
drive (FDD).
 Floppy disks, initially as 8-inch (200 mm) media and
later in 5 1⁄4-inch (133 mm) and 3 1⁄2-inch (90 mm) sizes,
were a ubiquitous form of data storage and exchange
from the mid-1970s well into the 2000s.[1]
 By 2010, computer motherboards were rarely
manufactured with floppy drive support; 3 1⁄2-inch floppy
disks can be used with an external USB floppy disk
drive, but USB drives for 5 1⁄4-inch, 8-inch and non-
standard diskettes are rare or non-existent, and those
formats must usually be handled by old equipment.
 While floppy disk drives still have some limited uses,
especially with legacy industrial computer equipment,
they have been superseded by data storage methods
with much greater capacity, such as USB flash drives,
portable external hard disk drives, optical discs, memory
cards and computer networks.

CD ROM
 A CD-ROM /ˌsiːˌdiːˈrɒm/ is a pre-pressed
optical compact disc which contains data. The
name is an acronym which stands for "Compact
DiscRead-Only Memory". Computers can read
CD-ROMs, but cannot write on the CD-ROM's
which are not writable or erasable.
 Until the mid-2000s, CD-ROMs were popularly
used to distribute software for computers
and video game consoles. Some CDs,
called enhanced CDs, hold both computer data
and audio with the latter capable of being played
on a CD player, while data (such as software or
digital video) is only usable on a computer (such
as ISO 9660 format PC CD-ROMs).

DVD ROM
 DVD (sometimes explained as "digital video disc" or "digital
versatile disc"[5][6]) is a digital optical disc storage format,
invented and developed byPhilips, Sony, Toshiba,
and Panasonic in 1995. DVDs can be played in many types of
players, including DVD players. DVDs offer higher storage
capacity than compact discs while having the same dimensions.
 Pre-recorded DVDs are mass-produced using molding
machines that physically stamp data onto the DVD. Such discs
are known as DVD-ROM, because data can only be read and
not written or erased. Blank recordable DVD discs (DVD-
R and DVD+R) can be recorded once using a DVD recorder and
then function as a DVD-ROM. Rewritable DVDs (DVD-
RW, DVD+RW, and DVD-RAM) can be recorded and erased
multiple times.
 DVDs are used in DVD-Video consumer digital video format and
in DVD-Audio consumer digital audio format, as well as for
authoring DVD discs written in a special AVCHD format to
hold high definition material (often in conjunction with AVCHD
format camcorders). DVDs containing other types of information
may be referred to as DVD data discs.

USB PEN DRIVE
 A USB flash drive is a data storage device that includes flash
memory with an integrated Universal Serial Bus (USB)
interface. USB flash drives are typically removable and
rewritable, and physically much smaller than an optical disc.
Most weigh less than 30 grams (1.1 oz).[1] As of January 2013,
drives of up to 512 gigabytes (GB) were available.[2] A one-
terabyte (TB) drive was unveiled at the 2013 Consumer
Electronics Show and became available later that
year.[3] Storage capacities as large as 2 TB are planned, with
steady improvements in size and price per capacity
expected.[4] Some allow up to 100,000 write/erase cycles,
depending on the exact type of memory chip used, and a 10-
year shelf storage time.[5][6][7]
 USB flash drives are often used for the same purposes for
which floppy disks or CDs were used, i.e., for storage, back-up
and transfer of computer files. They are smaller, faster, have
thousands of times more capacity, and are more durable and
reliable because they have no moving parts. Additionally, they
are immune to magnetic interference (unlike floppy disks), and
unharmed by surface scratches (unlike CDs). Until about 2005,
most desktop and laptop computers were supplied with floppy
disk drives in addition to USB ports, but floppy disk drives have
been abandoned due to their lower capacity compared to USB
flash drives.

BLUE RAY DISK
 Blu-ray Disc (BD) is a digital optical disc data storage format designed to
supersede the DVD format, in that it is capable of storing high-definitionvideo
resolution (1080p). The plastic disc is 120 mm in diameter and 1.2 mm thick, the
same size as DVDs and CDs.[4] Conventional (pre-BD-XL) Blu-ray Discs contain
25 GB per layer, with dual layer discs (50 GB) being the industry standard for
feature-length video discs. Triple layer discs (100 GB) and quadruple layers
(128 GB) are available for BD-XL re-writer drives.[5] The name Blu-ray Disc refers
to the blue laser used to read the disc, which allows information to be stored at a
greater density than is possible with the longer-wavelength red laser used
for DVDs. The major application of Blu-ray Discs is as a medium for video
material such as feature films. Besides the hardware specifications, Blu-ray Disc
is associated with a set of multimedia formats. Generally, these formats allow for
the video and audio to be stored with greater definition than on DVD.
 High-definition video may be stored on Blu-ray Discs with up to 1080p resolution
(1920×1080 pixels), at up to 60 (59.94) fields per second. The older DVD discs
had a maximum resolution of 480p (NTSC, 720×480 pixels) or 576p (PAL,
720×576 pixels).
 The format was developed by the Blu-ray Disc Association, a group representing
makers of consumer electronics, computer hardware, and motion pictures. Sony
unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype
player was released in April 2003 in Japan. Afterwards, it continued to be
developed until its official release in June 2006. As of June 2008, more than
2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with
3,500 in the United States and Canada.[6] In Japan, as of July 2010, more than
3,300 titles have been released.[7]

MEMORY CARD
 A memory card or flash card is an
electronic flash memory data storage
device used for storing digital
information. They are commonly used
in many electronic devices,
including digital cameras, mobile
phones, laptop computers, MP3
players and video game consoles.
Most of these can be diminutive, re-
recordable, and can retain data without
power.

MEMORY CARD
 PC Cards (PCMCIA) were among first commercial memory card
formats (type I cards) to come out in the 1990s, but are now
mainly used in industrial applications and to connect I/O devices
such as modems. In the 1990s, a number of memory card
formats smaller than the PC Card arrived,
including CompactFlash, SmartMedia, and Miniature Card. The
desire for smaller cards for cell-phones, PDAs, andcompact
digital cameras drove a trend that left the previous generation of
"compact" cards looking big. In digital cameras SmartMedia and
CompactFlash had been very successful[neutrality is disputed]. In 2001,
SM alone captured 50% of the digital camera market and CF had
captured the professional digital camera market. By 2005
however, SD/MMC had nearly taken over SmartMedia's spot,
though not to the same level and with stiff competition coming
from Memory Stick variants, as well as CompactFlash. In
industrial and embedded fields, even the venerable PC card
(PCMCIA) memory cards still manage to maintain a niche, while
in mobile phones and PDAs, the memory card market was highly
fragmented until 2010 when micro-SD came to dominate new
high-end phones and tablet computers.

MEMORY STICK
 Memory Stick is a removable flash memory
card format, launched by Sony in October
1998,[1] and is also used in general to
describe the whole family of Memory Sticks.
In addition to the original Memory Stick, this
family includes the Memory Stick PRO, a
revision that allows greater maximum
storage capacity and faster file transfer
speeds; Memory Stick Duo, a small-form-
factor version of the Memory Stick (including
the PRO Duo); and the even
smaller Memory Stick Micro (M2). In
December 2006 Sony added the Memory
Stick PRO-HG, a high speed variant of the
PRO to be used in high-definition video and
still cameras. Memory Stick cards can be
used in Sony XDCAM EX camcorders via
the MEAD-SD01 adapter.[2]

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